Add settings log, graphs, and model augmentation to sample.py

[klei22]

Several upgrades for sample.py:

• increased block size (context length), necessary for testing and verifying both FIRE and rotary embeddings.
• settable num_angles for symmetric rope variation
• graphs and images to illustrate next token generation
• each time sample.py runs, a folder in the same directory as the ckpt.pt file will be created with settings and (optional) graphs of the inference